Coated type magnetic recording media obtained by coating a dispersion of magnetic powders such as .gamma.-Fe.sub.2 O.sub.3, Co-doped .gamma.-Fe.sub.2 O.sub.3, .gamma.-Fe.sub.3 O.sub.4, CrO.sub.2, Berthollide compounds of Co-doped .gamma.-Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4, etc., or ferromagnetic metal alloy powders etc., in an organic binder such as vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, epoxy resin, polyurethane resin, etc., on a non-magnetic support and drying the coated layer have been widely used in the past.
However, with the recent increasing demand for higher recording densities, various attempts have been made to provide thin metal film type magnetic recording media where a thin film of ferromagnetic metal formed by a vapor deposition method such as vacuum vapor deposition, sputtering or ion plating, by a plating method such as electro-plating or electroless plating, etc., is used for the magnetic recording layer in which no binder is used.
For thin metal film media of this type there is no need to mix an organic binder in the magnetic layer and thus the packing density of the magnetic material is increased and the magnetic layer can be made considerably thinner (for example 0.05 to 0.3 .mu.m) than in the case of a coated type medium. Hence it is to be expected that media of this type will be of importance for the realization of more compact, high density recording media.
Of the methods used for forming thin metal film magnetic layers on a support, the vapor deposition method is suitable for the manufacture of media which have a large surface area, such as tapes, since the build-up speed of the film can be high with this method.
The oblique vapor deposition method described in U.S. Pat. Nos. 3,342,632 and 3,342,633 etc. is known as a method for the manufacture of magnetic films which have coercive force and squareness ratio.
Moreover, supports which have a very smooth surface are used for such thin metal film type media and excellent electromagnetic conversion characteristics are ensured. However, in this case, the contact area between the magnetic layer and the magnetic head and parts of the running system is increased and the coefficient of friction is increased, and problems arise with running durability.
The provision of very small protrusions on the surface of the magnetic layer in order to reduce the contact area, as indicated in JP-A-59-42638 for example, has been suggested. (The term "JP-A" herein used means an unexamined published Japanese patent application.) However, practical running properties and durability are not obtained by simply using these methods.
Attempts have also been made to improve running properties and durability by means of lubricating layers consisting of organic compounds which are provided on the surface of the magnetic layer and very small protrusions (JP-A-60-93636 and JP-A-61-11921).
Also, sulfur based extreme pressure agents have been suggested as lubricants which have a high adhesive force for the magnetic layer (JP-A-61-178718).
However, there are problems with running durability at low humidity even when a protective lubrication layer consisting of lubricants of the type mentioned above has been provided and, in practice, "still" durability is inadequate and head contamination and head blockage occur on repeated running.
The use of fluorine base polyetheres which have a --C.sub.n F.sub.2n O-- unit as a skeleton and polar terminal groups as lubricants has also been suggested (U.S. Pat. No. 4,268,556). However, satisfactory "still" durability and high repeat running passes are not obtained even when lubricants of this type are used on thin ferromagnetic film type magnetic recording media, and head contamination continues to occur.